1. Field of the Invention
The invention relates generally to voice communication and more particularly to systems and methods for side-tone noise suppression in a communication handset.
2. Background
In ordinary conversation, an individual speaker is accustomed to hearing the words they speak. This type of “feedback” provides certain queues to the speaker such as whether they are speaking loudly enough to be heard, what there tone is, etc. But when a speaker speaks into a telephone or other type of handset, e.g., a wireless communications handset, at least part of this feedback is blocked by the handset itself. This blocking can create an unnatural, and uncomfortable, experience for the speaker, because they do not receive the normal queues that allow them to evaluate how effectively they are communicating.
To compensate, communication handsets typically incorporate side-tone processing, which transfers a portion of the signal spoken by the user back into the handset earpiece. Thus, the side-tone signal replaces the normal feedback, which is blocked by the handset. In addition to providing normal communication queues as described above, the side-tone signal ensures the user that their handset is working and that they are speaking into, or loud enough for, the handset.
Unfortunately, however, current handsets do not filter out noise in the side-tone signal. Thus, if the speaker is in a noisy environment, the noise gets transferred to the speaker's ear. The noise can substantially degrade the effectiveness of the feedback because, for example, the user can no longer tell whether they are speaking loud enough. In fact, in such a situation, the user is likely to overcompensate for the noise they hear and speak too loudly into the handset. Also, the noise can interfere with the speaker's ability to hear the other party to the conversation. The result is an unpleasant experience for both parties. Moreover, the speaker is often forced to repeat himself, or is forced to ask the other party to repeat himself, which leads to increased talk time. Increased talk time is not only inconvenient, but for wireless communication handsets at least, is undesirable because it also drives up the charges incurred by the user.
The noise also gets transferred to the party on the other end of the call. As a result, conventional handsets typically include some mechanism whereby the noise is suppressed in the outgoing communication. But this noise suppression does not extend to the side-tone audio path in conventional handsets. Therefore, surrounding noise is still fed back to the user's ear, even in handsets with noise suppression on the outgoing communication, or reverse link.